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<p><span lang="EN-US">The forms of occurrence of vanadium metal are determined by the major chemical reactions in the aquatic environment such as hydrolysis, oxidation, reduction, and precipitation. Depending on pH, potential and total concentration of inorganic ions and organic ligands, vanadium compounds may undergo various transformations to produce a whole range of chemical forms in aqueous systems. In this paper, a novel approach has been applied for calculating potential</span><span lang="EN-US">-</span><span lang="EN-US">pH (Pourbaix) diagrams, based on the developed thermodynamic analysis of chemical equilibria in the V–H₂O system. On the basis of currently revised thermodynamic data for V(III), V(IV) and V(V) hydrolysis and original thermodynamic and graphical approach used, the repartition of their soluble and insoluble chemical species has been investigated. By means of ΔG–pH diagrams, the areas of thermodynamic stability of V(IV) and V(V) hydroxides have been established for a number of analytical concentrations of vanadium in heterogeneous mixtures. The obtained results, based on the thermodynamic analysis and graphic design of calculated data, are in good agreement with available experimental data.</span></p>

Microbial synthesis of nanoparticles has a potential to develop simple, costeffective and eco-friendly methods for production of technologically important materials. In this study, for the first time a novelactinomycete strain Streptomyces glaucus71 MD isolated from a soy rhizosphere in Georgiais for the first time extensively characterized and utilized for the synthesis of silver nanoparticles. Scanning Electron Microscope (SEM) allowed observing extracellular synthesis of nanoparticles, which has many advantages from the point of view of applications. Production of silver nanoparticles proceeded extracellularlywith the participation of another microorganism, bluegreen microalgae Spirulinaplatensis (S. platensis). In this study it is shown that the production rate of the nanoparticles depends not only on the initial concentration of AgNO 3 but also varies with time in a nonmonotonic way. SEM study of silver nanoparticles remaining on the surface of microalgae revealed that after 1 day of exposure to 1 mM AgNO 3 nanoparticles were arranged as long aggregates along S. platensiscells strongly damaged by silver ions. However, after 5 days of exposure to silver S. platensiscells looked completely recovered and the nanoparticles were distributed more uniformly on the surface of the cells.

The study aimed to contribute to the scarce data on concentrations in the soft tissue of wild mussels growing in coastal cities of South Africa. The intake of 26 micro and macroelements was estimated. The mass fractions of sample sets from 8 sites along the South African coast from the West (Port Nolloth) to the East (Durban) were studied by neutron activation analysis at the Joint Institute for Nuclear Research (Russia). The following elements were identified as potentially hazardous due to high consumption risks: Al, Cr, Co, Zn, As, and I at stations in the Cape Town area (Waterfront, Hout Bay) and Durban. The mean concentrations of these elements among all individuals were 208, 0.8, 0.46, 60, 2.6, and 11 ppm of wet weight, respectively. In the studied mussels, the concentrations of Cr, Zn, As, and Se (ranging between 0.2− 2.8, 14-290, 1.6− 4.6, and 0.31− 2.4 ppm of wet weight, respectively) exceeded maximum permissible levels for fish products. The weekly consumption of more than 250 g of fresh mussels per person could increase the risk for human health by potential intake of such elements as Al, As, and I.

The methods of synthesis of silver (Ag) nanoparticles by the cyanobacteria Spirulina platensis and Nostoc linckia were studied. A complex of biochemical, spectral, and analytical methods was used to characterize biomass and to assess changes in the main components of biomass (proteins, lipids, carbohydrates, and phycobilin) during nanoparticle formation. The size and shape of Ag nanoparticles in the biomass of both types of cyanobacteria were determined. Neutron activation analysis was used to study the accumulation dynamics of the Ag quantity. The analytical results suggest that the major reduction of Ag concentration in solutions and the increase in biomass occur within the first 24 h of experiments. While in this time interval minor changes in the N. linckia and S. platensis biomass took place, a significant reduction of the levels of proteins, carbohydrates, and phycobiliproteins in both cultures and of lipids in S. platensis was observed after 48 h. At the same time, the antiradical activity of the biomass decreased. The obtained results show the necessity of determining the optimal conditions of the interaction between the biomass and the solution containing Ag ions that would allow nanoparticle formation without biomass degradation at the time of Ag nanoparticle formation by the studied cyanobacteria.

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